In a pneumatic tire, a groove extending in the tire circumferential direction is formed in a tread surface to ensure drainage in the rain and the like. In order to improve drainage of such a pneumatic tire and prevent occurrence of hydroplaning, various proposals have hitherto been made in terms of arrangement of grooves in the tread surface and the like. In those proposals, there is a pneumatic tire in which a curved inclined groove which is formed in the tread surface is provided with a protruded rim extending in the groove longitudinal direction in the bottom of the groove to rectify water having flowed into the groove and thus improve the drainage (for example, see the Japanese Patent Laid-Open publication No. 2000-318411).
It is true that when the protruded rim extending in the groove longitudinal direction is provided in the bottom of the groove as described above, reduction of the drainage due to turbulence of the water flow can be avoided. However, it is not possible to obtain an effect of positively discharging water having flowed into the groove to the exterior. Accordingly, the capability of preventing hydroplaning has not necessarily been sufficient.